Process of separating solvents from substances.



' Patented Oct. 28, I902.

" No. 7|2,4os.

. F. e. nunuur. PROCESSOF SEPARATING SOLVENTS FROM SUBSTANCES.

(Application filed July 11, 1902.5

(No Model.)

INVENTOB 29 WITNESSES ATTORNEYS m: nunhls msns co mora'urnon WASHINGYON, u c.

UNITED STATES PATENT )FFIC E FRANCIS G. DU PONT, OF WILMINGTON, DELAWARE.

PROCESS OF SEPARATING SQLVENTS FROM SUBSTANCES.

SPECIFICATION formingpart of Letters Patent No. 712,406, dated October 28, 1902.

Application filed July 11, 1902. Serial No. 115,117. (No specimens.)

To all whom it may concern:

Be it known that I, FRANCIS G. DU PONT, a

citizen of the United States, residing at Wil-f lowing to be a full, clear, and exact description of the same, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to a process of freeing nitrocellulose from alcohol-etheiy and is particularly intended for use in the manufacture of smokeless powder for extracting the solvent used in colloiding nitrocellulose.

My invention consists in the novel method of extracting thesolvent, as hereinafterdescribed, and in the novel steps of the process.

The objects of my invention are to faciliate the extraction of solvents from nitrocellulose, I

action of a solvent, usually alcohol-ether,

and much difficulty is experienced in extracting the solvent after the completion of the I colloiding action in order that the powderor coating effectively resists the escape of.

further portions of the solvent from the interior of the blocks or grains, so that the solvent from theinterior can escape only very slowly. cellulose powder ofith'e sizes used in ordnance requires several months fordrying, the exact time dependinglargely on the size andshape of the, grains. By the process herein described I prevent the formation of such a In practice it is found that nitro hard outer coating while the interior is still saturated with the solvent and in addition free the nitrocellulose substantially completely from the solvent by a relatively brief treatment, so that after such treatment the drying may be comparatively rapid. In the accompanying drawing I illustrate diagramatically an apparatus which may be used for the carrying out of the process. Said apparatus may consist of a vessel 1,

adapted to contain the material to be treated, having at the top a filling-orifice 2, adapted .tO. be closed by a suitable'plug, andhaving at the bottom apipe 3, through which air may be admitted or liquid contents of the "essel permitted to drain olf, said pipe being providedwith aregulatiug-valve 4/ From the upper portion of the vessel a pipe 5 may lead to-asuction pump 6, and thence another pipe Tmay lead to a condenser S. V

In carrying out my process I place nitrocellulose saturated with the alcohol-ether in the vessel 1 and then introduce alcohol into the said vessel. As is well known, although alcohol-ether readily dissolves nitrocellulose of the higher degrees of nitration neither alcohol nor ether by itself is a solvent of the higher grades of nitrocellulose. Since ether dissolves in alcohol in all proportions, when the nitrocellulose saturated with alcohol-ether is submerged in an excess of alcohol the ether diffuses itself through the main body of alcohol in the vessel. I then proceed to draw off the ether from the vessel, which may be done in various ways, one of the most convenient being to open the valve 4: slightly and then by means of the suction-pump 6 to draw air upward through the body of alcohol cellulose, it follows that when the latter is re- .cohol is not in itself a solvent of the nitromoved from the alcohol-bath surface drying will not cause the formation of a hard film or skin upon its surface, through which the interior liquid can only escape very slowly, but, on the contrary, the alcohol still within the grains will be left free to evaporate and escape therefrom and will so escape quite rapidly.

While the ether is being taken off, as above described, the apparatus may be maintained at or slightly below the boiling temperature of ether either by maintaining the room in which the apparatus is located at about such temperature or by applying heat to the outside of the vessel 1 in any other suitable wellknown way, and, if necessary, by heating the air entering the pipe 3. The only purpose of heating the air or the vessel 1 is to supply the heat absorbed by the liquid within the vessel 1 in its evaporation and to maintain the temperature of such liquid at about the point at which the ether will evaporate most readily. The exhaust from the suction-pump may be led to a suitable condenser and the ether and alcohol carried thereby condensed and saved.

By this process I have found that nitrocellulose may be substantially freed from ether after about one days treatment in the manner described and that when the powder is removed from the vessel and spread out to dry four or five days drying suffices to dry and harden it, Whereas by the former methods of removing the solvent by evaporation into the air several months are required ,for drying, and in addition the solvent is lost.

Instead of maintaining the room in which the operation is conducted at or near the boiling temperature of ether at atmospheric pressure or of applyingheat to the vessel or to the entering air the vacuum pump 6 may be caused to reduce the pressure in vessel 1 considerably below atmospheric pressure, thus lowering the boiling temperature of the ether to substantially ordinary atmospheric temperature or even lower. In the latter case it is not necessary to admit air.

In the ordinary method of drying for :removing the solvent from nitrocellulose powders the powder-grains dry most rapidly at the ends, and this causes uneven shrinking of the grains and considerable deformation thereof. This is not the case with powder from which the solvent has been removed by the method above described.

It is obvious that the air admitted through the tube 3 and which in bubbling up through the alcohol carries off with it ether dissolved therein is a mere vehicle for carrying off the ether and that other gases might be used instead of air, if desired. This air will necessarily carry off some alcohol, since alcohol evaporates slowly at ordinary atmospheric temperatures; but the proportion of alcohol carried off with respect to the other will be very small, and this step of the process amounts, in eifect, to a separation of the other from alcohol. The vapors carried off are caught in the condenser and there condensed, so that the ether may be used over again.

It is obvious that my process may be varied to a considerable extent in carrying it out, and I do not limit myself to the particular details of the process herein described.

What I claim is 1. The herein-described process of extracting from nitrocellulose a solvent comprising a plurality of ingredients, which separately are not solvents of nitrocellulose, which consists in subjecting such nitrocellulose and solvent to the action of an excess of one of the ingredients of such solvent.

2. The herein-described process of extracting from nitrocellulose a solvent comprising a plurality of ingredients, which separately are not solvents of nitrocellulose, which consists in flooding such nitrocellulose and solvent with an excess of one of the ingredients of the solvent.

3. The herein-described process of extracting alcohol-ether from nitrocellulose, which consists in flooding the nitrocellulose carrying the alcohol-ether with an excess of alcohol.

4. The herein-described process of extracting alcohol-ether from nitrocellulose, which consists in immersing nitrocellulose carrying the alcohol-ether in alcohol and causing a gas to pass through the alcohol, thereby carrying off the ether in solution therein.

In testimony whereof I aftix my signature in the presence of two witnesses.

FRANCIS Gr. DU PONT. Witnesses:

REUBEN SATTERTHWAITE, J r., CLIFFORD V. MANNERING. 

